This proposal is a continuation of our research program to establish the role of acrosomal enzymes and microtubules in fertilization in the environment created by the oviduct. Our recent research has demonstrated an organized distribution of proteinase in the acrosomes of rabbit, rhesus monkey, and human spermatozoa, the deposition of proteinase in distinct sites in the penetration tunnel through the zona pellucida, and the presence of microtubules with a distribution pattern similar to the proteinase of the acrosome. Our immediate goals are to establish the morphology of this microtubule system, the mechanism by which it transports proteinase to its site of action, and the biochemistry of the oviduct fluid that affects polymerization or depolymerization of this labile micotubule system. We have also resumed our research on the proteinase inhibitors of oviduct fluid, especially the acrosin inhibitors, to establish their physiological role in controlling fertilization in mammals.